A plurality of voters now opposes further U.S. military action in Libya, and most say President Obama needs congressional approval to continue those operations.

A new Rasmussen Reports national telephone survey finds that just 26% of Likely U.S. Voters feel the United States should continue its military actions in Libya. Forty-two percent (42%) are opposed and 32% are undecided. (To see survey question wording, click here.)

But 59% agree the president should get the approval of Congress if he wants to continue U.S. military action in Libya. Twenty-one percent (21%) say congressional approval is not needed. Another 20% are not sure.

This marks a jump in support for congressional authorization from mid-March just after the president committed U.S. military forces to helping anti-government rebels in Libya. At that time, 47% said the president should have gotten congressional approval before ordering the military into action in Libya. Thirty-four percent (34%) said the prior approval of Congress was not necessary, but 19% were undecided.

Most voters remain skeptical of how soon U.S. military involvement in Libya will end. Just 32% think it is at least somewhat likely that U.S. military operations in Libya will be over by the end of the year, with 10% who say it is Very Likely. Fifty-four percent (54%), however, think it is unlikely those operations will be done by the close of the year, including 14% who say it is Not At All Likely. Another 14% are not sure.

The survey of 1,000 Likely Voters was conducted on June 10-11, 2011 by Rasmussen Reports. The margin of sampling error is +/- 3 percentage points with a 95% level of confidence. Field work for all Rasmussen Reports surveys is conducted by Pulse Opinion Research, LLC. See methodology.

The House of Representatives last week passed a measure requiring the president to come back with a full report on military actions in Libya by the end of the month. A second measure with bipartisan support calling for an end to the Libyan mission was defeated.

The president insists that NATO allies like Great Britain and France are now taking leading military operations in Libya, with the United States taking a back seat since the early weeks of the campaign. U.S. voters aren’t so sure: 38% believe the military operations in Libya are being handled primarily by U.S. allies like England and France, but 32% think the United States is primarily in charge.

Fifty percent (50%) of Republicans and a plurality (46%) of voters not affiliated with either major party believe the United States should end its military action in Libya. Democrats are more narrowly divided, but 41% of those in the president’s party are undecided.

Sixty-four percent (64%) of GOP voters and 68% of unaffiliateds feel the president should get the approval of Congress if he wants to continue military action in Libya. A plurality (47%) of Democrats agrees.

Most Republican and unaffiliated voters think an end to U.S. military action in Libya is unlikely by the end of the year. Democrats are evenly divided on the question.

The majority (54%) of Political Class voters, on the other hand, think U.S. military involvement in Libya is likely to be over by the end of the year. Sixty percent (60%) of Mainstream voters say it’s unlikely.

While 48% of Political Class voters support continued military action in Libya, 49% of those in the Mainstream do not. Sixty-four percent (64%) of Mainstream voters believe the president needs congressional approval to continue operations in Libya, but the Political Class is closely divided.

At the same time, overall voter confidence in U.S. efforts in the War on Terror remain at record high levels since the killing of Osama bin Laden. However, voters appear less optimistic about the situations in both Afghanistan and Iraq.